Abstract: The surface of a semiconductor wafer is cleaned simultaneously using diluted hydrofluoric acid and electrolytic ionized water. The electrolytic ionized water is produced using an electrolyte supplied into an intermediate cell of a 3-cell electrolyzer. The 3-cell electrolyzer has an anode cell, the intermediate cell, and a cathode cell partitioned from one another by ion exchange membranes. After deionized water is supplied into the anode cell and the cathode cell and the intermediate cell is filled with an electrolytic aqueous solution, electrolysis is carried out to produce electrolytic ionized water. The electrolytic ionized water and the hydrofluoric acid solution are then supplied to one or more semiconductor wafer cleaning apparatus. The simultaneous use of the electrolytic ionized water and the diluted hydrofluoric acid offers an improvement in removing contaminants from the surface of the wafer without damaging an insulating layer or a metal layer exposed at the surface of the semiconductor wafer.